The preocular tear film plays an essential role in maintaining ocular surface integrity, protecting against microbial challenge and preserving visual acuity. Tear film dysfunction, in turn, may severely impact the eye and lead to desiccation, ulceration and perforation of the cornea, an increased incidence of infectious disease, and pronounced visual impairment and blindness. Countless people suffer from tear film disorders, which are termed dry eye syndromes and are classified into 2 major types: aqueous-deficient and evaporative. Aqueous-deficient dry eye is due to decreased tear secretion from the lacrimal gland. An example is Sjogren's syndrome, a common autoimmune disease that afflicts primarily women and destroys the lacrimal gland. Evaporative dry eye is typically caused by meibomian gland dysfunction and may be a major cause of dry eye during menopause, use of estrogen replacement therapy and aging. The long range objectives of this grant application are to test our hypotheses that: (1) sex steroids are extremely important in the physiological regulation of the ocular surface and adnexa, as well as the production of the tear film;and (2) sex, sex steroid hormones, and in particular androgen deficiency, are critical etiologic factors in the pathogenesis of both aqueous-deficient and evaporative dry eye syndromes. Experimental procedures include mouse models, whole genome microarrays (e.g. gene chips), real-time-PCR, in situ hybridization, cell cultures, immunoassays, 2D gels, MALDI/mass spectrometry, enzyme assays, histology, image analysis, hormone reconstitution experiments, as well as use of a controlled environment chamber. Our specific aims are to: (1) identify the genes and proteins that mediate the sex-related differences in, and the sex steroid control of, lacrimal and meibomian glands in normal and/or autoimmune (i.e. Sjogren's syndrome) mice;(2) examine the influence of sex and sex steroids on the development of dry eye;and (3) identify the sex-related differences that exist in the gene expression of the human lacrimal and meibomian glands, cornea and conjunctiva. Results from these studies should significantly advance our understanding of the processes by which sex and sex steroids influence the anterior segment of the eye. In addition, findings may have health relatedness for the eye, because they: (1) explore the regulation of the tear film; and (2) may lead to the development of specific therapies for the clinical treatment of dry eye syndromes.